Review: Sony FE 100-400mm f/4.5-5.6 GM OSS lens
When you consider it was way back in 2013 that Sony debuted their full frame a7, it's remarkable that it wasn't until the middle of 2017 that the Japanese company offered any native lens for FE mount longer than 200mm.
In hindsight it is likely that Sony saw shorter focal lengths like the 16-35mm, 24-70mm and 70-200mm as more pressing priorities to convince DSLR users to make the full frame mirrorless switch. However with the April announcement of the Sony a9 last year all that changed.
Seemingly aware they would have a hit on their hands if they released a suitable telephoto to match the a9's super fast 20fps drive speed, the Sony FE 100-400mm f/4.5-5.6 GM OSS lens was announced at the same time as the company's flagship mirrorless camera. Since then, we've seen the announcement of the monster FE 400mm F2.8 GM OSS, but that fast f/2.8 aperture comes at a cost that puts it out of reach of all but the most well off photographers.
The Sony FE 100-400mm f/4.5-5.6 GM OSS (I'll call it the 100-400mm from now on for brevity) is a much more practical focal length than its 400mm prime brother for sports and general purpose wildlife photographers, but can also be used in a pinch for portraiture and event photography too.
I've been using the lens for the past month in a variety of conditions, in the rainforest and sandy beaches of Queensland's Fraser Island, the hot dusty environment of Kakadu National Park in the Northern Territory, and in my backyard in the Blue Mountains, NSW. I've used it with my own a7III, and was supplied the 100-400mm by Sony Australia for this review.
The lens
Sony's professional quality G Master range carries with it an expectation of uncompromising image quality, build and autofocus. The 22 element / 16 group optical design in the 100-400mm includes one Super ED and two ED glass elements to minimise chromatic aberration while maximising resolution. Inside, you'll also find a sonic-type (Direct Drive SSM) motor for fast and silent autofocus with a minimum focus distance of 0.98m.
The lens features optical image stabilisation (said to reduce camera shake by up to five stops), a dust and splash-proof barrel, customisable focus-hold buttons, a stiffness adjustment for the zoom ring, and the lens is compatible with both the SEL14TC (1.4x) and SEL20TC (2.0x) teleconverters.
The build
Out of the box the lens weighs 1400g, a bit lighter than Canon's EF 100-400mm f/4.5-5.6L IS II USM lens (1600g). The front element fits 77mm front filters, and the included reversible lens hood features a cutout window that allows the adjustment of a circular polariser if you decide to use one. Sony also includes a detachable tripod foot, mounted to a rotating collar, along with a padded bag for transportation.
The front element is coated with fluorine, which helps to prevent oil and water from sticking to the glass, and makes it easy to wipe away fingerprints and rain drops. The texturised rubber manual focus ring sits behind this front element. Interestingly there's a tension adjustment ring right behind the zoom control. When set to its tightest position you can still zoom, however it requires a bit more pressure on the zoom ring and the front element won't creep out when the lens is pointing downwards.
On the looser setting the zoom ring moves with much more freedom, but you may find lens creep becomes an issue. As you might expect, the sweet spot is somewhere in the middle – if you're shooting erratically moving subjects moving towards you and then away (like birds), the loosest setting is your best bet. For almost every other subject matter, keeping it about halfway is a good balance.
There are three focus hold buttons—at 12, 3, and 6 o'clock—in the space between the focus and zoom rings. Holding any of them fixes the autofocus—useful if shooting a static subject, but not a feature I found myself using often. These three buttons can be reassigned in the menu if you so wish, with Eye-AF being a popular choice.
Whether it was my shooting style or the design of the lens I'm not sure, but I did find the side of my index finger would occasionally bump the button at 6 o'clock, suddenly stopping my autofocus in its tracks. However this was easily corrected by adjusting my hold on the lens.
On the left side closer to the mount you'll find a selection of switches. From top to bottom these are an AF/MF toggle switch, and a focus limiter that allows you to either let the lens hunt for focus across its full range or speed focus if you're shooting distant subjects from three meters to infinity. Below this is an Optical Steady Shot (OSS) switch that allows you to turn on or off the in-lens stabilisation system, and finally a switch that allows you to set the OSS to Mode 1, for shots when you're not moving the camera, or Mode 2, for situations where you're panning.
OSS also works in conjunction with in-body stabilisation if your camera supports it, giving 5 stops of stabilisation. In practice this means longer shutter speeds hand held and steadier footage if shooting video, something really useful if you're shooting at the 400mm end of the focal range. I found it particularly useful when shooting from a shaky boat in Kakadu in low light.
The last piece of the puzzle is the weather sealing. I could only find a relatively thin rubber gasket at the rear end of the lens, which does suggest that the lenses' weather sealing isn't as well implemented as on Canon's 100-400mm. Any lens that changes volume when focussed or zoomed, and this one grows in length when it is zoomed, is by definition not sealed. If this is an issue to you, it is something worth considering.
Autofocus
If you're shooting wildlife, accurate autofocus is critical for capturing fast moving subjects. Although modern autofocus systems are miles better than anything we had even 10 years ago, the true test of any camera's AF is when you pair it with good glass and use it in challenging conditions. For wildlife photographers this typically means low light and busy backgrounds, both of which I sought out to really put the 100-400mm through its paces.
Early adopters of Sony's A-series cameras keen to shoot at telephoto focal lengths had no option but to adapt third party lenses to their mirrorless bodies. My experience of using adapted telephoto lenses with both Metabones and Sigma's popular MC-11 adapters has certainly been more miss than hit, and I'd argue that choosing native glass is more important than ever when an accurate autofocus system can be the difference between getting the shot or missing it entirely.
This meant my expectations were high with the 100-400mm, and I'm happy to say the overall focusing performance was superb, with the lens snapping into focus quickly, and also speedily identifying and locking onto subjects. This is most likely down to the combination of two focussing motors working in tandem, with one focus group driven by a double-linear motor, and a second by a Direct Drive Supersonic Motor (DDSSM).
In the middle of the day with a single subject in the frame against an uncomplicated background like the sky, the lens focussed almost instantaneously and rarely let go.
As the light dropped and backgrounds became busier, like the conditions I found shooting from a boat in Kakadu National Park at sunset, I still found the autofocus rarely missed. This included shooting an azure kingfisher at the waters edge as it sat perched on a complex background of tree branches, and low-flying Great Egrets flying just above long grass and in front of and behind trees.
Autofocus accuracy was also impressive at higher frame rates, like this series of a backlit Great Egret landing on a tree branch captured at 8fps. The autofocus had no trouble holding the egret in focus, even with the background and tree coming into frame.
The only flying subjects I struggled with were Welcome Swallows on Fraser Island, but these birds fly incredibly fast and having a good technique is just as important as fast AF for capturing them. For every other bird subject, I found the autofocus tenacious and thoroughly reliable.
Sharpness
Image sharpness on the Sony 100-400mm is excellent. Performance is consistent throughout the zoom range, with corners retaining plenty of sharpness right up to 400mm. At the widest aperture of f5.6 and all the way to f11, images are very sharp, and it's a testament to the lens that I never felt I needed to stop down to improve sharpness. Hit your focus, and you can rest assured your images will retain plenty of detail.
Vignetting is also minimal, and if you shoot at apertures smaller than f8 you'll rarely notice it. As lens technology has matured I've found vignetting is something I now rarely consider. All modern telephotos are excellent at managing vignetting even at wider apertures, and even if it is present, correcting it in post is relatively painless. But if this is still something you're conscious of, I found the 100-400mm managed it very well, displaying about a stop of vignetting at f5.6.
The Sony 100-400 also manages flare very well. Like with any lens you can find a way to produce this effect if you try hard enough, however if you're shooting into a light source and don't want it to distract from your images you can expect it to be well controlled with the 100-400mm.
Although a lens like this would probably not be your first pick for macro work, the minimum focussing distance of 0.98m means it can also be very useful for detail shots. These soldier crabs on Fraser island are about the size of a thumbnail and are particularly sensitive to movement – quickly burrowing down into the sand at the slightest vibration.
To capture images of the crabs involved crouching on the beach and not moving for more than half an hour, waiting for them to assume the coast was clear and emerge from the sand. I wanted to fill the frame with the crabs, and so it meant waiting for them to get as close as possible to me to get the shot at 400mm. It's only after I took the shots I realised how close they were. Once I stood up they quickly disappeared, no doubt stunned a big scary photographer was so close.
Finally Bokeh is pleasant, although somewhat busy when dealing with complex backgrounds. However considering the minimum aperture of f5.6, it's certainly not distracting.
Overall
If you're in the market for an all-round wildlife and sports telephoto lens for Sony E mount it's hard to look past the 100-400mm f/4.5-5.6 GM OSS lens. It displays excellent autofocus, contrast and sharpness throughout the zoom range and from corner to corner. When paired with a suitable body with in-built image stabilisation, like Sony's a9 or A7R III, it will help you get excellent images even when shooting fast moving subjects in challenging lighting at the extreme end of its focal range.
The only concern I have with the 100-400mm is the weather sealing. Knowing the tendancy of lenses that grow as the focal length is increased to have weather-tightness issues, the lenses ability to be a workhorse in challenging shooting environments is not something I'm 100% confident about. But if the subjects you shoot are not found in bad weather, you'll find the the Sony FE 100-400mm f/4.5-5.6 GM performs brilliantly, with excellent features alongside fantastic image quality. I can recommend it highly.